This invention relates to the field of character recognition, and is especially applicable to magnetic ink character recognition (MICR) systems for reading documents which are printed with magnetic ink characters.
In the processing of documents encoded with magnetic ink character recognition (MICR) characters, it has been recognized that for increased processing efficiency it is desirable to reduce as much as possible the reject rate, that is the frequency at which the read head and associated recognition logic are unable to recognize a character as being a valid member of the character set. The processing of rejects requires manual intervention which reduces operating efficiency and increases the cost of document processing. In order to lower the reject rate, it has been proposed to use dual read systems, typically employing two different types of read heads which have different characteristics and capabilities in reading the characters, so that if the first read head is unable to recognize a character, the recognition of that character by the second read head would thus result in a successful reading of that document and would thereby lower the reject rate. Once such dual read head recognition system is disclosed in U.S. Pat. No. 3,938,089 issued Feb. 10, 1976.
A factor which has not been addressed by prior character recognition systems is the comparative economic consequences of rejects and substitution errors. While the manual processing of "rejects" reduces efficiency and increases costs, it is far more costly to correct undetected "substitution errors" (i.e. where the recognition logic incorrectly reads a character and substitutes an incorrect character for the correct character). In the case of processing checks for example, documents containing substitution errors pass through the system undetected may not be discovered until much later, for example after the check has been sent to another bank or has been posted incorrectly to a customer's account. At this later time, it is much more costly to correct the error. The cost of manually correcting a substitution error can be from 50 to 100 times the cost of manually correcting a reject. However, substitution errors occur with significantly less frequency than rejects. The present invention is based upon a consideration of the economic impact of substitution errors and rejects in order to provide greater overall efficiency in the operation of the document reading system. Moreover, as will be apparent from the explanation which follows, the present invention employs a novel and somewhat unconventional approach in achieving this improvement in overall cost efficiency.